Perennial, but probably not very long-lived.
Solitary herb with a moderately stout tap root, branched, brown or white; a caudex 0.2–0.8 cm thick ending in one or more rosettes up to 5–10 cm wide on stout branches. One or several erect, simple flowering stems 2–10 cm tall with several leaves, densely pubescent with white, articulate, floccose hairs. The species of Pedicularis are semi-parasites, partly depending on nutrients from other species through root connections.
Leaves alternate. Rosette leaves up to 3–5 cm; petioles about as long as blade, narrowly winged; blades nearly linear in outline, pinnatifid to pinnatisect, lobes crenate or shallowly to moderately lobed, sparsely hairy. Lower stem leaves sheath-like with reduced lobes and broadened mid vein, glabrous or with very sparse white, floccose, articulate hairs. Middle stem leaves similar to leaves of vegetative rosettes but with short petioles, hirsute.
Inflorescence a short, dense, bracteate raceme with 5–10 (or more) flowers on short pedicels. Lower bracts much longer than flowers, upper bracts about as long as flowers, pinnately divided with broadened mid rib. Petioles of bracts broadly winged and constitute ca. 2/3 of the length of bracts.
Flowers monosymmetric, erect. Calyx fused, tubular, with 5 obtuse to acute teeth, moderately two-lipped, strongly pubescent with long, floccose hairs. Corolla 0.8–1.3 cm, with a tubular fused part and a two-lipped limb. Lower lip three-lobed with the side lobes broader than the mid lobe, glabrous. Upper lip narrowly galeate (helmet-shaped), glabrous. Stamens 4, 2 short and 2 longer. Gynoecium of 2 fused carpels with a single style and a globular stigma. Stamens and stigma not protruding from the corolla tube.
Fruit a one-roomed, falcate capsule 10–12 × 3–5 mm, opening at the top and with many seeds. Seeds small and brown.
Sexual reproduction by seeds; no vegetative reproduction. The plant flowers regularly and seems to be little damaged by bad weather as the flowers are partly protected by the pubescence. The flowers are adapted to pollination by flower-specific insects. It has been assumed that the genus Pedicularis is obligately pollinated by bumble-bees (the genus Bombus). No representatives of this insect group are present in Svalbard. It is probable that the main pollinators are flies and it is also probable that many flowers self-pollinate. Fruit-set is regular. Seed germination is up to 20 % both in laboratory and field (Alsos et al. 2013; Müller et al. 2011).
The stiff stems and the apical opening of the capsule are adaptations to ballistic dispersal.
The two Svalbard species of Pedicularis – P. dasyantha and P. hirsuta – differ in size (P. dasyantha is larger, especially the flowers), density of pubescence (P. dasyantha is much more hairy), flower shape and pubescence (P. dasyantha has hairy flowers, P. hirsuta glabrous ones), and somewhat in ecology (P. dasyantha usually occupies drier sites than P. hirsuta, but they often grow close to each other). Digging up the plants, the roots of P. dasyantha are distinctly yellow (when fresh), whereas those of P. hirsuta are white or brownish. The seeds of P. dasyantha have a fluffy white seed coat that acts as a sponge to catch rain water, whereas the seeds of P. hirsuta are small and brown.
Most common in moderately to densely vegetated herb-mats and heaths, moist tundra, and on patterned ground. Due to being semi-parasitic on other plant species, P. hirsuta hardly survives in sparsely vegetated environments. Usually on mixed soils, moderately drained or moist. Largely indifferent as to soil reaction (pH) but perhaps avoiding the areas with the most acidic substrates. Requires a minimum of snow protection during winter, but plants germinating from seeds the same spring are often seen also on exposed sites. Probably little grazed by reindeer and geese.
Frequent or common in the middle and northern arctic tundra zones and transgressing into the polar desert zone in several places. Occurs in all sections. Found on all major islands except for Bjørnøya, common on Spitsbergen.
The general range is broadly amphi-Atlantic in the arctic zones and reaching south to mountains in the northern boreal zone, in Europe to N Fennoscandia.
Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.
Müller, E., Cooper, E.J. & Alsos, I.G. 2011. Germinability of arctic plants is high in perceived optimal conditions but low in the field. – Botany 89: 337–348.